This invention relates to a sensing apparatus, and more particularly to such an apparatus for underground drum cutter mining machines having cutter drums with at least a sensing member projecting radially beyond a fixed pick element positioned at an advanced position from the sensing member such that the sensing member undergoes radial loading and produces a corresponding signal for use by a control to respond to radial movements of the tool and to determine the height through which the cutter drum is provided.
West German Patent No. 1,173,049 discloses a drum cutter for use in winning operations, opening out operations and drifting operations in minerals, particularly the coal and surrounding rock. The cutter drums are provided with toothed striking rollers on the periphery of the drum for operative use in both directions of rotation by the cutter drum. The toothed striking rollers are rotatably mounted with their axes parallel to the roller axes or askew thereof. The toothed rollers are carried by holders on the drum at laterally, spaced-apart locations in a ring or spiral pattern.
West German Patent No. 521,979 discloses the use of a fork to rotatably mount a disc forming a roughing or marking cutter for association with a cutting pick. The object of this construction of parts is to break out the mineral which has been marked by the roughing or marking cutter by means of the pick which contacts the mineral after the marking cutter and thereby reduces the formation of dust.
Other mining machines known in the art include devices to provide a continuous indication of the position of a rotary cutter head relative to the various layers of ore while the cutting head is performing the material releasing operations. More specifically, such a device as shown in West German Patent No. 916,043 provides a testing or detecting tooth resiliently mounted in a rubber sleeve in the cutter head for use when making the starting cut in the layers of ore. The testing or detecting tooth is connected to a pressure detector which converts the test-tooth pressure variations into electrical signals which are, in turn, displayed relative to polar coordinates on an image screen of a cathode-ray oscillograph. The pressure detector is designed to respond to substantially only the vibrations produced during cutting by the pressures imposed on the test tooth. The pressure detector changes resistance at cadence of the vibration and, through the agency of the oscillograph, provides a visual indication corresponding to the frequency and amplitude of the test-tooth vibrations which are used to control the cutting head.
West German Patent No. 1,939,956 discloses a device for indicating the hardness of the ore during the extraction process with a rotating cutting device of a mining machine. The hardness indicator is associated with the rotating cutting device wherein the indicator comprises a sensing pick or the like resiliently mounted in a holder that includes means to respond to movements of the sensing pick as produced by variations in the ore hardness. Electrical signals produced by the hardness indicator are used to control the height of the cutter drum. The sensing pick is disposed after and close to a fixedly-mounted pick so that the sensing pick remains in a constant depth within the ore during the removal process. Such a device provides satisfactory measured values only when the cutting edge of the pick is sharp but the measured values become inaccurate when the cutting edge has become blunt or broken either after prolonged use or because of heavy stressing of the cutting edge by the rock surrounding the ore seam.